The Performance Advisor monitors queries that MongoDB considers slow
and suggests new indexes to improve query performance. The Performance
Advisor recognizes a query as slow if it takes longer than 100
milliseconds to execute. For the selected host and time period, the
Performance Advisor evaluates up to the 20,000 most recent slow queries
found in the logs.

Recommended indexes are accompanied by sample queries, grouped by query shape,
that were run against a collection that would benefit from
the suggested index. The Performance Advisor is always enabled and does
not negatively affect the performance of your Atlas clusters.

Note

To view field values in a sample query in the Performance
Advisor, you must be a user with at least one of the following
access:

Indexes improve read performance, but a large number of indexes can
negatively impact write performance since indexes must be updated during
writes. It is important to consider this tradeoff when deciding whether
to create new indexes for a collection that already has several. Examine
whether a query for such a collection can be modified to take advantage
of existing indexes, as well as whether a query occurs often enough to
justify the cost of a new index.

The Performance Advisor displays sample queries with recommended
indexes. Each sample query includes a query inefficiency score, which is
how many documents were read for every document returned by the query.
A score of 1 represents a very efficient query because every document read matched
the query and was returned with the query results. The Performance Advisor
displays a warning icon next to any score over 1,000, which represent
highly inefficient queries. All suggested indexes represent an opportunity
to improve query performance.

Select the time period from the list box for which you want to view data.¶

The Performance Advisor displays up to 20 query shapes
across all collections in the cluster and suggested indexes for those
shapes.

Note

The Performance Advisor collects existing indexes for collections
with slow queries every six hours. However, the Performance
Advisor generates indexes based on actual queries within five
minutes of query execution. It is possible to see suggestions for
indexes that you have already created, but these are removed the
next time that the Performance Advisor collects indexes.